This invention concerns fuel injectors for controllably injecting fuel into the intake manifold or cylinders of automotive engines. Fuel injection occurs when a small diameter needle valve is lifted from a valve seat to allow pressurized fuel to spray out through a valve seat orifice and into the engine where it vaporizes.
It has heretofore been recognized that preheating of the fuel during cold starting will greatly reduce emissions caused by incomplete fuel vaporization during cold starts.
Various heater arrangements have been proposed, including an external heater jacket on the injector body, a heater internally of the injector, such as described in copending U.S. Ser. No. 08/627,707, now U.S. Pat. No. 5,758,826, as well as U.S. Pat. Nos. 4,458,655; 3,868,939 and 4,898,142. Another approach is a heater element downstream of the valve seat, on which fuel is sprayed when the valve injector opens, such as described in U.S. Pat. Nos. 4,627,405 and 4,572,146.
An advantageous arrangement is an internal heater just upstream of the valve seat as described in copending U.S. Ser. No. 08/627,707, filed on Mar. 29, 1996now U.S. Pat. No. 5,758,826, which maximizes the heating of the fuel that occurs just prior to injection. In this arrangement, the presence of the heater does not affect the spray pattern, as may occur with the downstream heaters referenced above. Coking problems also arise where heated surfaces are not continuously wet with fuel, as in these downstream heaters.
Complications are encountered in providing electrical connections to a heater located in an internal location where the fuel is present, as electrical conductors must extend from the electrical plug connection where no fuel is present into the space above the valve seat where pressurized fuel from the rail is present. This necessitates a sealing arrangement to prevent the escape of fuel past the conductor.
An object of the present invention is to provide an improved internal fuel injection heater and also arrangements for establishing reliable electrical connections to such internal heater, as well as mountings for the heater structure within the fuel injector.